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Pharynx Region commonly known as the throat An intersection that leads either to the esophagus or trachea As we swallow, the larynx (voice box) moves upward & tips the epiglottis (flap of cartilage) over the opening of the trachea Sect 21.6

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Heimlich Maneuver

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Esophagus Conducts food from the pharynx down to the stomach Peristalsis – wavelike contraction of the smooth muscles of the digestive tract that squeezes the bolus down to the stomach (sect 21.4) Sect 21.8

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Sphincter Valves on Stomach Cardiac sphincter is at the top of the stomach Prevents backflow into esophagus Pyloric sphincter is at the bottom of the stomach Regulates passage of chyme into small intestine

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Stomach (cont.) Takes about 2-6 hours to empty the stomach of a meal Mucus coats stomach & protects it from the corrosive effects of digestive juices

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Stomach Ulcers Gastric ulcers are open sores that develop on stomach wall Some ulcers develop from too much pepsin &/or acid, or too little mucus Some ulcers develop from bacterial infections that cause a loss of mucus & damage the stomach lining Sect 21.10

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Small Intestine Most of the chemical digestion of macromolecules in food take place Nutrients are absorbed into the blood Sect 21.11

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Nucleic Acid Enzymes Nucleases – hydrolyze nucleic acids into their component nucleotides What are nucleic acids? What is a nucleotide?

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Fat Enzymes Fats are 1st coated w/bile salts to keep them separated from one another - known as emulsification Lipase then breaks down fat droplets into fatty acids & glycerol

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Specialized in absorbing nutrients, wrinkles w/in the small intestine give it a large surface area, wrinkles are covered by small, fingerlike projections called villi Parts of Small Intestine (Jejunum & Ileum)

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- each villus has tiny surface projections called microvilli - microvilli extend into the interior of the intestine Tiny lymph vessels extend directly into core of the villus along w/the capillaries (lymph vessels & capillaries pick up nutrients) - known as the lacteal p. 439

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Capillaries that drain nutrients away from the villi converge into larger blood vessels, which eventually lead to the liver the liver converts many nutrients into new substances that the body needs

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One arm of the T is a blind pouch - cecum - appendix (a small fingerlike projection of the cecum) has a minor contribution to immunity - appendix is prone to infection itself

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Function of the colon is to reabsorb water if water used during digestion is not reclaimed, severe dehydration would result wastes are called feces feces are stored in the rectum until they can be eliminated

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Essential Nutrients The body cannot make 9 of the 20 amino acids needed to make proteins - must be obtained from the diet and cannot be stored in excess - meat & animal by-products (eggs, milk, cheese) Sect 21.16